Does current thread have the exclusive access to newly allocated inode?
The chanllege comes from individual filesystem's ->alloc_inode method.
It may exposure the inode to private lists, thus give other threads a chance
to access the inode.
That should not happen, however, because the inode is not even gone through a
basic initialization. The locks may not be initialized yet, the inode is not
ready for parallel access.
Thus, from getting an inode from alloc_inode(), till we put it on a list and
that list becomes accessible, we can safely manipulate the inode without
taking i_lock.
This patch fixes three places that take the unnecessary i_lock.
Note in iget5_locked(), I have no strong proof set() should not put the inode
into private lists. Any suggestion?
Signed-off-by: Guo Chao <y...@linux.vnet.ibm.com>
---
fs/inode.c | 6 ------
1 file changed, 6 deletions(-)
diff --git a/fs/inode.c b/fs/inode.c
index ac8d904..d2d15aa 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -895,9 +895,7 @@ struct inode *new_inode_pseudo(struct super_block *sb)
struct inode *inode = alloc_inode(sb);
if (inode) {
- spin_lock(&inode->i_lock);
inode->i_state = 0;
- spin_unlock(&inode->i_lock);
INIT_LIST_HEAD(&inode->i_sb_list);
}
return inode;
@@ -1015,10 +1013,8 @@ struct inode *iget5_locked(struct super_block *sb,
unsigned long hashval,
if (set(inode, data))
goto set_failed;
- spin_lock(&inode->i_lock);
inode->i_state = I_NEW;
hlist_add_head(&inode->i_hash, head);
- spin_unlock(&inode->i_lock);
inode_sb_list_add(inode);
spin_unlock(&inode_hash_lock);
@@ -1082,10 +1078,8 @@ struct inode *iget_locked(struct super_block *sb,
unsigned long ino)
old = find_inode_fast(sb, head, ino);
if (!old) {
inode->i_ino = ino;
- spin_lock(&inode->i_lock);
inode->i_state = I_NEW;
hlist_add_head(&inode->i_hash, head);
- spin_unlock(&inode->i_lock);
inode_sb_list_add(inode);
spin_unlock(&inode_hash_lock);
--
1.7.9.5
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